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questions about solar kilns

Started by farmfromkansas, February 02, 2019, 08:50:12 PM

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farmfromkansas

Went shopping this evening, Menards has twinwall polycarbonate 4x8- 6 mill for 42.99 per sheet.  8 mill is special order and twice as much.  Is 6 mill heavy enough? Also, saw a post Dr. Gene posted saying air movement is not necessary below 20% mc.  Does that mean turn off the fans once your moisture content goes below 20%?
Most everything I enjoy doing turns out to be work

scsmith42

Quote from: farmfromkansas on February 02, 2019, 08:50:12 PM
Went shopping this evening, Menards has twinwall polycarbonate 4x8- 6 mill for 42.99 per sheet.  8 mill is special order and twice as much.  Is 6 mill heavy enough? Also, saw a post Dr. Gene posted saying air movement is not necessary below 20% mc.  Does that mean turn off the fans once your moisture content goes below 20%?
I've found that double pane 8mm allows me an extra couple of months of SK drying as opposed to single pane.
In my kilns I use a humidistat to turn the fans off when the MC% falls below 20%.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

xlogger

Scott, I was looking at a timer switch for my solar kiln but after reading your post I looked on Amazon for a humidistat switch. Can you put green wood in kiln and does it cut off at night?
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

farmfromkansas

The 6 mill IS twinwall, or double pane, if you will, just wondered what others are using. When using your humidistat, does it turn your fans on at night?
Most everything I enjoy doing turns out to be work

GeneWengert-WoodDoc

Although air speed no longer controls the speed of drying under about 20% MC, you do need some air flow to bring heat in and to carry moisture away from the lumber.  So, maybe 150 or 200 rpm.  Oftentimes, really low air affects other aspects of the kiln.

The issue with plastic covers is the U-V degradation, and possible damage from hail.  All else being equal, 6 mil is fine, unless you are in a hail area, where the extra strength could possibly help.  But, it might not be strong enough anyway.  So, I would use 6 mil.  Just make sure there is some comment about its outside stability when exposed to sunlight.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

scsmith42

Quote from: xlogger on February 03, 2019, 06:05:08 AM
Scott, I was looking at a timer switch for my solar kiln but after reading your post I looked on Amazon for a humidistat switch. Can you put green wood in kiln and does it cut off at night?
I have a separate timer that controls turns the kiln fans on in the morning and off at night.  
Yes, you can go into a SK with green wood, "but", it's not always wise.  Just about an 4/4 species I'll put in green.  8/4 WO may get a month or two of air drying first, OR I may cover part of the collector to reduce the drying rate for the first month or two in order to reduce surface checking.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

GeneWengert-WoodDoc

The original Virginia Tech solar kiln that I designed in 1978us a timer for the fans. Turn on whenthere issoar heating (about 9AM) and off about 7PM when the heat inside drops and there is no sunlight entering the kiln.  
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

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